Lamedon was a region and fiefdom in southern Gondor; a series of valleys through which the Ciril river flowed south. It was one of the most densely populated regions in Gondor. At the time of the War of the Ring its lord was Angbor.
During that war, Angbor did not send any soldiers to Minas Tirith during the initial assault, as he chose to defend instead the southern city of Linhir, which rested near the mounds of the river Gilrain. He held off the Southron assailants coming from the Harad and the Haven of Umbar for a long while. The only men Minas Tirith received from Lamedon were some scattered woodsmen.
At the time Aragorn passed through Lamedon with the Grey Company, the Army of the Dead drove forth the assailants from Linhir, though the staunch defenders fled as well. But Angbor alone remained and braved the fear of the Dead. Then Aragorn bade him gather his folk and follow them. But the Grey Company departed first, and by the time Angbor joined them with all the horsemen he could muster, the Corsairs of Umbar had been driver forth, and the Dead released. But many of the men of Lamedon, as well as soldiers from Lebennin and various other southern fiefs, came on the Corsairs to Minas Tirith, where they bore themselves bravely in battle. But Angbor, leading four thousand, went by land, coming to garrison Minas Tirith after the hosts departed for the Black Gate and the ensuing Battle of the Morannon.